Recovery of calcium oxalate from the bark of trees



Patented Feb. 10, 1925.

UNITED STATES PATENT OFFICE.

WILLIAM ADOLF FRAYMOUTH, OF BHOPAL, INDIA, ASSIGNOR TO THE BHOPAL PRO- DUGE TRUST LIMITED, OF BHOPAL, CENTRAL INDIA, A CORPORATION OF BHOPAL STATE.

RECOVERY OF CALCIUM OXALATE FROM THE BARK OF TREES.

No Drawing.

To all whom it may concern:

Be it known that I, WILLIAM ApoLr FRAY- MOUTH, a subject of His Majesty Klng George V, and resident of Bhopal, Bhopal State, Central India, chemical englnecr, have invented certain new and useful Improvements in the Oxalate from the Bark of Trees, the following is a specification.

This invention relates to the recovery of calcium oxalate and other substantially 1nsoluble oxalates from trees.

The bark of the Termimlia arjuna (known under the names Arjun, Urjoon, Kahua, Koha) is known to contaln tannin and other water-soluble matter. We have now found that the bark of the Termc'na lia arjum and of other trees also contains crystalline calcium oxalate. Other trees which are found to contain calcium oxalate are hereinafter referred to as like trees.

Thepercentage of calcium oxalate conof which tained in the bark of these trees varies considerably, but in the dry bark of the Tarmz'nah'a a'rjuna tree up to 50% by we ght may exist. This natural crystalline calc1um oxalate differs from the calcium oxalate as, generally known. The latter is an amorphous precipitate while the former appears in a c stalline form, but both can be converted y the addition of sulphuric acid or other re-agents into oxalic acid br other oxalates.

According to this invention, a process for obtaining calcium oxalate or other substantially insoluble oxalates consists in extracting the crystalline calcium oxalate from the Termdnalia crjwna or like trees.

Accordin to this invention, the first step is to take t e bark from the tree; and the crystalline calcium oxalate is extracted therefrom. The bark employed may be live bark or the dead scabs or flakes from the bark of the trees, or the bark or root bark can be taken from fallen trees.

Preferably, according to this invention, a process for obtaining calcium oxalate or other substantially insoluble oxalates consists in taking the bark of the Terminalz'a arjzma or like trees, crushing it sufficiently Recovery of Calcium late.

Application fll'ed July 17, 1923. Serial No. 652,006.

sists in crushing it finely, removing fibrous matter; thereafter extracting with water to remove soluble substances, and finally subjecting the material to physical concentra tion so as to obtain crystalline calcium oxa- The physical concentration may be effected by subjecting the powdered material 1n a dry condition to the action of an air current for example an air-current separator, or by winnowmg or like method. 7

Again, the physical concentration may be effected b subjecting the crushed material (preferab y after extraction of the tannin) to water concentration of the kind employed for the concentration of ores, e. g. by jigs, vanners, shaking tables, spitzkasten, centrifugal separators, classifiers and the like.

A preferred process acording to this invention for obtaining calcium oxalate or other substantially insoluble oxalates consists in taking the bark from the Temimalz'a arjzma or like trees, crushing it finely to liberate contained crystals of calcium oxa late from the remainder, (preferably removing fibrous matter), extracting with water to remove soluble substances and subjectmg the residue in aqueous suspension to the action of a centrifugal separator with impervious basket to separate out the calcium oxalate.

The following is a description of various methods of carrying this invention into practical effect. As'already stated, the first step in the process of recovering calcium rom prior to oxalate from the Terminalz'a arjum or like trees consists in taking the bark from the tree.

The bark is then crushed or ground up into a fine powder. The fibrous part of the bark when separated contains little or no tannin or calcium oxalate. It is preferable, therefore, to separate the fibrous matter from the cementing matters, secretions, gums, and other non-fibrous portions which are rich in tannin and calcium oxalate, by a process which is already known in the extraction of tannin from bark.

The pulverulent residue may be subjected to the action of an air current for the purpose of separatin those particles which are readily suspende in the air current from the calcium oxalate particles (which are heavier than the other portions of the bark and fall more readily through the air).

It is preferable to employ wet methods of concentration. The bark is first crushed to a fine powder, say to 100 mesh to the linear inch. Unless this fine crushing is carried out, all the cells are not-opened up and the finest particles of oxalate are not liberated. As already stated, the fibrous parts may then be se arated. In any event t e crushed materiaPor fine powder extracted therefrom is then made into a pulp with water and the oxalate iecovered therefrom by wet concentration methods. Any of the water gravity separators, such as spitzkasten,jigs,buddles, log-washers, vanners, concentrating tables,

-' classifiers, or the like may be used. The

fineness of crushing which is desirable may make it diflicult to separate the finest particles, but some of the latest slime concentra tors used for the treatment of ores can successfully be used for this purpose, such as those which have mechanical contrivances for removal of heavier materials after settlement, while at the same time lighter materials are floated ofi.

Good results can be obtained by wet concentration in a centrifugal separator with an im ervious basket.

t is diflicult to extract all the calcium oxalate unless practically all the tannin and other soluble contents of the bark have been extracted first. In the bark of the Terminalz'a arjuma the amount of tannin and other soluble constituents is large. amounting to about 32% of the weight of the bark. The presence of the tannin increases the specific gravity of the cells of the bark and thus renders separation by gravity methods from the heavier calcium oxalate crystals less easy.

It is therefore preferred to carry out the process in the following manner The dry bark of the Terminaha aryum or like trees is crushed to a powder fine enough to liberate as far as possible all the crystals from the cells in the bark. This is preferably done in known manner by crushmg and beating the. material so that the fibrous part (which contains little or no tannin or oxalate) is broken up into wool and separated from the cementing matter, secretions, gums or other non-fibrous substance. The powdered bark is then wetted with a minimum of water in a suitable apparatus. After transference to the said apparatus some of the oxalate, being heavler than the rest of the pulp, may be removed either intermittently or continuously, during the running of the plant. i

The pulp with as little water or liquor as posslble is then mixed thoroughly to an even cream-like consistency, and passed into a centrifugal machine with 1m ervious walls. The walls inay conveniently lined with detachable plates on which the solid matter is deposited and by means of which it may be readily removed. An almost riect separation takes place, for the oxa ate being heavier than the bark residue is all deposited in the outside precipitation layer of the centrifugal machine. The bark residue or refuse is deposited in the next layer and the tannin llquor passes out of the machine free from bark residue or oxalate. On stopping the machine and removal of the plates the oxalate and the bark residue may be removed separately.

Having now particularly described and ascertained the nature of my said invention and the manner the same is to be performed, I declare that what I claim is I 1. A process for obtaining substantially insoluble oxalates consisting in taking the bark of trees containing thesaid oxalates, crushing it sufliciently finely to liberate contained oxalate crystals, and subjecting the resulting material to physical concentration to separate out the oxalate.

2. A process for obtaining substantially insoluble oxalates according to claim 1 wherein prior to concentration soluble matters in the bark are extracted therefrom.

3. A processfor obtaining calcium oxalate according to claim 1, wherein prior to concentration tannin in the bark is extracted therefrom.

4. A process for the treatment of the bark of trees containing substantially insoluble oxalates consisting in crushing it finely to liberate the oxalate crystals, removing fibrous matter, thereafter extracting with water to remove soluble substances and finally subjecting the material to physical concentration so as to obtain crystalline calcirm oxalate. 5. A process according to claim 1 wherein the physical concentration is efiected by subjecting the crushed material to water gravity separation.

6. A process for obtaining substantially insoluble oxalates consisting in taking. the

bark of trees containin the said oxalates, In testimon whereof I hereto afiix my crushin it dryito a fine y granulated condisignature in t e presence of two witnessa, 10 tion to iberate the oxalate crystals, extractthis 23d day of February, 1923.

ing the soluble matter with water, regrind l ing the residues in a wet condition to a size W IAM ADOLF FRAYMOUTH- less than 60 mesh and subjecting the result- Witnesses: ing material to ph sical concentration to L. H. DALE,

separate out the oxa ate. R. F. CLARK. 

